Port 512Rexec
Rexec (Remote Execution Daemon) is a service traditionally used on UNIX systems allowing users to execute commands on a remote machine over a network. It facilitates remote process execution by authenticating with a username and password sent in plain text, which poses significant security risks. While once commonly adopted in trusted internal environments for remote management, Rexec has largely been superseded by more secure technologies due to its inherent vulnerabilities..
- transport
- tcp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 10,392
single transport
payload readable on path
registered with iana
caution
rank 436 of 993 · top 44%
1 other service is registered on port 512. compare all 2 →
Technical Details
what runs on :512Rexec operates as part of the r-command suite on UNIX systems, which also includes rlogin and rsh. It enables a client system to authenticate and request command execution on a remote host running the rexecd daemon over TCP port 512. The client initiates a connection, supplies credentials, and specifies the command to execute, with the output sent back over the network.
The protocol itself is straightforward but lacks negotiation or encryption layers, relying instead on plaintext communication. It forfeits modern safeguards in favor of simplicity and low overhead, making it suitable in trusted, closed network environments historically. The daemon listens continuously on port 512, accepting authenticated requests and executing commands with the provided user context.
Technically, Rexec provides a basic but risky remote shell facility and process execution method. Its design origins predate advanced security concepts like encrypted tunnels and robust access control, which today renders it unsuitable except in the most controlled legacy scenarios or testing labs.
Security Information
exposure of :512risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
remote access averages 4.0 across 110 ports — this one sits level with it.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp
every listening transport is another surface to filter at the edge
security overview
Common Vulnerabilities:
- Credentials are transmitted in clear text, making interception trivial for network eavesdroppers.
- Lacks built-in encryption or data integrity verification, exposing command data and responses.
- Potential avenue for unauthorized access or privilege escalation if the rexecd daemon is improperly configured.
- Susceptible to man-in-the-middle attacks that exploit plaintext credentials or inject malicious commands.
Common Mitigations:
- Replace Rexec with secure alternatives like SSH, which provides encrypted remote command execution.
- Disable rexecd service entirely in production environments to eliminate its attack surface.
- Use network segmentation and firewall rules to restrict access to port 512.
- Employ intrusion detection systems to flag unexpected rexecd activity.
- Enforce strong authentication policies and avoid plaintext logins over insecure networks.
Related Ports
the 8 most looked-up other ports in remote access — 110 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :8000 | Intel Remote Desktop / Alternate HTTP Port | TCP | Web Services | safe | 84.3k |
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| :8291 | Winbox MikroTik Admin | TCP | Security | caution | 62.9k |
| :8008 | IBM HTTP Server Admin | TCP | Web Services | caution | 58.3k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :23 | Telnet | TCP | Remote Access | caution | 34.8k |
risk mix of the 8 listed
- safe13%
- caution88%
0 of 8 encrypted